IDeally, you wont be in the tub for hours. But of course, it does happen! Getting in too soon can stall labor, so its best to wait until active labor or transition to get in, when it will help speed things up Of course, some moms who are having a tough early labor, want to slow things down for a break, so its not necessarily a bad thing.

Now, you can get warmers for tubs. Personally, I didnt. I used the La Bassine, which is insulated pretty decent. We filled it slightly warmer than I would have wanted. Then, on top of that, most pg women are hot anyways, and even more so in labor. So cooler water isnt so bad. But you do want to make sure its not COLD, b/c baby will need to be warm Its hard to get it too cool though. I could imagine a winter birth in a drafty house might be a problem though.

With that said.... we didnt use a warmer. My DH filled up a little warmer to begin with, then as it cooled off over 2 hours, hed add a little more water. He didnt fill it up too much, so he was able to add to it without it spillign over If wed have gotten too close to being "full" - he simply could have taken a bit out, then put a little in. (We used a bucket to remove water, and a hose hooked up to he nearest sink to put water in).